Acute fatiguing effects and biomechanical characteristics of a single bout eccentric quasi-isometric resistance exercise of ankle plantar flexors

IntroductionInvestigation of the eccentric quasi-isometric (EQI) resistance exercise has started in recent years. However, the biomechanical characteristics and fatigue effects of EQI muscle actions in the ankle plantar flexors remain unexplored. This study aimed to compare the biomechanical charact...

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Main Authors: Luka Križaj, Nejc Šarabon, Žiga Kozinc
Format: Article
Language:English
Published: Frontiers Media S.A. 2025-06-01
Series:Frontiers in Bioengineering and Biotechnology
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Online Access:https://www.frontiersin.org/articles/10.3389/fbioe.2025.1517098/full
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author Luka Križaj
Nejc Šarabon
Nejc Šarabon
Nejc Šarabon
Žiga Kozinc
author_facet Luka Križaj
Nejc Šarabon
Nejc Šarabon
Nejc Šarabon
Žiga Kozinc
author_sort Luka Križaj
collection DOAJ
description IntroductionInvestigation of the eccentric quasi-isometric (EQI) resistance exercise has started in recent years. However, the biomechanical characteristics and fatigue effects of EQI muscle actions in the ankle plantar flexors remain unexplored. This study aimed to compare the biomechanical characteristics of plantarflexion EQIs and post-EQI acute fatigue between two different loading intensities.MethodsTwenty regularly physically active participants (9 men, 11 women) completed 3 sets comprising of a single EQI muscle contraction at 75% and 90% (one intensity for each leg in a random order) of maximal voluntary isometric contraction (MVIC) on an isokinetic dynamometer. Outcome variables included total contraction time, torque impulse, angular velocities and range of motion during EQI muscle actions, as well as pre- and post-contraction MVIC measures.ResultsThe analysis indicated no statistically significant effect of EQI muscle-action on MVIC torque (main effect of time: p = 0.636). There were also no statistically significant differences between EQI muscle actions performed at 75% and 90% MVIC regarding angular velocity (p = 0.244). However, executing EQI muscle contraction at 75% MVIC resulted in statistically significantly larger total contraction time, total torque impulse, and range of motion (p < 0.001) compared to EQI at 90% MVIC.DiscussionThese findings suggest that performing EQI contractions at 75% MVIC may be more effective for generating greater mechanical stimulus without inducing significant acute fatigue.
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spelling doaj-art-3faf0bb7c6ca404384e8654a03fc4c6d2025-08-20T03:32:20ZengFrontiers Media S.A.Frontiers in Bioengineering and Biotechnology2296-41852025-06-011310.3389/fbioe.2025.15170981517098Acute fatiguing effects and biomechanical characteristics of a single bout eccentric quasi-isometric resistance exercise of ankle plantar flexorsLuka Križaj0Nejc Šarabon1Nejc Šarabon2Nejc Šarabon3Žiga Kozinc4Faculty of Health Sciences, University of Primorska, Izola, SloveniaFaculty of Health Sciences, University of Primorska, Izola, SloveniaAndrej Marušič Institute, University of Primorska, Koper, SloveniaLudwig Boltzmann Institute for Rehabilitation Research, St. Pölten, AustriaFaculty of Health Sciences, University of Primorska, Izola, SloveniaIntroductionInvestigation of the eccentric quasi-isometric (EQI) resistance exercise has started in recent years. However, the biomechanical characteristics and fatigue effects of EQI muscle actions in the ankle plantar flexors remain unexplored. This study aimed to compare the biomechanical characteristics of plantarflexion EQIs and post-EQI acute fatigue between two different loading intensities.MethodsTwenty regularly physically active participants (9 men, 11 women) completed 3 sets comprising of a single EQI muscle contraction at 75% and 90% (one intensity for each leg in a random order) of maximal voluntary isometric contraction (MVIC) on an isokinetic dynamometer. Outcome variables included total contraction time, torque impulse, angular velocities and range of motion during EQI muscle actions, as well as pre- and post-contraction MVIC measures.ResultsThe analysis indicated no statistically significant effect of EQI muscle-action on MVIC torque (main effect of time: p = 0.636). There were also no statistically significant differences between EQI muscle actions performed at 75% and 90% MVIC regarding angular velocity (p = 0.244). However, executing EQI muscle contraction at 75% MVIC resulted in statistically significantly larger total contraction time, total torque impulse, and range of motion (p < 0.001) compared to EQI at 90% MVIC.DiscussionThese findings suggest that performing EQI contractions at 75% MVIC may be more effective for generating greater mechanical stimulus without inducing significant acute fatigue.https://www.frontiersin.org/articles/10.3389/fbioe.2025.1517098/fulleccentric quasi-isometric contractionankle plantar flexorsintensityexerciseeccentric contraction
spellingShingle Luka Križaj
Nejc Šarabon
Nejc Šarabon
Nejc Šarabon
Žiga Kozinc
Acute fatiguing effects and biomechanical characteristics of a single bout eccentric quasi-isometric resistance exercise of ankle plantar flexors
Frontiers in Bioengineering and Biotechnology
eccentric quasi-isometric contraction
ankle plantar flexors
intensity
exercise
eccentric contraction
title Acute fatiguing effects and biomechanical characteristics of a single bout eccentric quasi-isometric resistance exercise of ankle plantar flexors
title_full Acute fatiguing effects and biomechanical characteristics of a single bout eccentric quasi-isometric resistance exercise of ankle plantar flexors
title_fullStr Acute fatiguing effects and biomechanical characteristics of a single bout eccentric quasi-isometric resistance exercise of ankle plantar flexors
title_full_unstemmed Acute fatiguing effects and biomechanical characteristics of a single bout eccentric quasi-isometric resistance exercise of ankle plantar flexors
title_short Acute fatiguing effects and biomechanical characteristics of a single bout eccentric quasi-isometric resistance exercise of ankle plantar flexors
title_sort acute fatiguing effects and biomechanical characteristics of a single bout eccentric quasi isometric resistance exercise of ankle plantar flexors
topic eccentric quasi-isometric contraction
ankle plantar flexors
intensity
exercise
eccentric contraction
url https://www.frontiersin.org/articles/10.3389/fbioe.2025.1517098/full
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